Nd, Sr and O isotopic study on the spilite-keratophyre sequence in Xiqiu shows that its ∈_(Nd) values are inthe range of 4.02-5.26, and its ∈_(Sr) values, +1.4-2.6. According to the points of these data in the ∈_(N...Nd, Sr and O isotopic study on the spilite-keratophyre sequence in Xiqiu shows that its ∈_(Nd) values are inthe range of 4.02-5.26, and its ∈_(Sr) values, +1.4-2.6. According to the points of these data in the ∈_(Nd)-T,∈_(Sr)-T and ∈_(Nd)-∈_(Sr) diagrams, the spilite-keratophyre is interpreted as being slightly contaminated by crustalmaterials. Its δ^(18)O values are 3.9-5.0‰. The depletion of ^(18)O in the rocks resulted from the influence ofseawater hydrothermal alteration during or soon after the rock formation. Based on the isotopic characteristicsand available geochemical data, it is believed that the spilite-keratophyre was formed in the well-developedisland-arc environment during the Late Proterozoic subduction of the palaeo-Pacific plate beneath thesoutheastern margin of the Yangtze massif.展开更多
The U-Th-40K concentrations of granite are on 1–2 orders of magnitude greater than those of basaltic-ultrabasic rocks. Radiogenic heat of a granitic melt has significant influence on the cooling-crystallization perio...The U-Th-40K concentrations of granite are on 1–2 orders of magnitude greater than those of basaltic-ultrabasic rocks. Radiogenic heat of a granitic melt has significant influence on the cooling-crystallization period of the melt. In this paper we derived a formula to calculate prolongation period (t A) of cooling-crystallization of a granitic melt caused by radiogenic heat. Calculation using this formula and radioactive element concentrations (U=5.31×10?6; Th=23.1×10?6; K=4.55%) for the biotite adamellite of the Jinjiling batholith shows that the t A of the adamellite is 1.4 times of the cooling period of the granitic melt without considering radiogenic heat from the initial temperature (T m=960°C) to crystallization temperature (T c=600°C) of the melt. It has been demonstrated that the radiogenic heat produced in a granitic melt is a key factor influencing the cooling-crystallization process of the granitic melt, and is likely one of the reasons for inconsistence between emplacement ages and crystallization ages of many Meso-Cenozoic granitoids.展开更多
文摘Nd, Sr and O isotopic study on the spilite-keratophyre sequence in Xiqiu shows that its ∈_(Nd) values are inthe range of 4.02-5.26, and its ∈_(Sr) values, +1.4-2.6. According to the points of these data in the ∈_(Nd)-T,∈_(Sr)-T and ∈_(Nd)-∈_(Sr) diagrams, the spilite-keratophyre is interpreted as being slightly contaminated by crustalmaterials. Its δ^(18)O values are 3.9-5.0‰. The depletion of ^(18)O in the rocks resulted from the influence ofseawater hydrothermal alteration during or soon after the rock formation. Based on the isotopic characteristicsand available geochemical data, it is believed that the spilite-keratophyre was formed in the well-developedisland-arc environment during the Late Proterozoic subduction of the palaeo-Pacific plate beneath thesoutheastern margin of the Yangtze massif.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40372036 and 40221301)
文摘The U-Th-40K concentrations of granite are on 1–2 orders of magnitude greater than those of basaltic-ultrabasic rocks. Radiogenic heat of a granitic melt has significant influence on the cooling-crystallization period of the melt. In this paper we derived a formula to calculate prolongation period (t A) of cooling-crystallization of a granitic melt caused by radiogenic heat. Calculation using this formula and radioactive element concentrations (U=5.31×10?6; Th=23.1×10?6; K=4.55%) for the biotite adamellite of the Jinjiling batholith shows that the t A of the adamellite is 1.4 times of the cooling period of the granitic melt without considering radiogenic heat from the initial temperature (T m=960°C) to crystallization temperature (T c=600°C) of the melt. It has been demonstrated that the radiogenic heat produced in a granitic melt is a key factor influencing the cooling-crystallization process of the granitic melt, and is likely one of the reasons for inconsistence between emplacement ages and crystallization ages of many Meso-Cenozoic granitoids.
